1. Field of the Invention
The present invention relates to a rubber track used for an undercarriage of a vehicle, and particularly to an improvement in a guide lug which protrudes from an inner peripheral surface of a rubber track.
2. Description of the Related Art
Generally, guide lugs are formed at equal pitch on the inner peripheral surface along the longitudinal direction of the rubber track. The functions of these guide lugs are to transmit the driving force from a sprocket to the rubber track and to prevent detracking of the rubber track from track rollers, i.e., to prevent the rubber track from coming-off of track rollers.
Particularly, when the rubber track is shifted laterally against track rollers due to lateral force, the track rollers and the guide lugs repeatedly contact each other and the force to bring the rubber track back to the original position is generated. In these cases, the friction between the guide lugs and track rollers causes detracking, and further, abrasion or breakage of the guide lugs.
FIGS. 14 and 15 each show an inner peripheral surface of a rubber track 11 in the state described above. FIG. 14 shows a structure in that a plurality of pairs of guide lugs 12, 12 are formed to protrude from an endless rubber elastic body.
A track roller 20 usually rolls straddling these guide lugs 12, 12. When the rubber track 11 is shifted laterally against the track roller 20, the track roller 20 contacts the guide lugs 12, 12 as indicated by the dotted line (only one side is shown) and further shift of the track roller 20 is restricted and the track roller 20 is brought back to its original rolling contact surface.
For this reason, large frictional force is applied particularly to outer side surfaces of the guide lugs 12, 12 and the rubber track is apt to detrack from the track rollers. And in some cases, abrasion or breakage may occur in the guide lugs.
On the other hand, FIG. 15 shows a rubber track having plurality of guide lugs 12 formed in a protruding manner on a single line along the longitudinal direction of the rubber track. In the same way as in the structure shown in FIG. 14, when the track roller 20 is shifted from a normal rolling position, the track roller 20 repeatedly contacts the guide lugs 12 as indicated by the dotted line to prevent the shift of the track roller 20. In this case as well, the rubber track is apt to detrack from the track rollers 20. According to circumstances, abrasion or breakage may occur in the guide lugs.
Further, when these guide lugs 12 are engaged with an unillustrated sprocket and are used for transmission of driving force, a sprocket pin and each guide lug 12 are constantly in a state of being rubbed against each other so that a base portion of the guide lug 12 particularly deforms. For this reason, not only the rubber track is apt to detrack from the track roller, but also abrasion or breakage is apt to occur in the base portion of the guide lugs 12. Particularly, when the guide lugs 12 are each formed of rubber, there is a strong tendency toward occurrence of these states.
In addition, when the track roller 20 contacts the guide lugs 12, large running resistance is generated and energy loss is thereby caused.